make crust: preheat oven to 350º with rack in the middle. stir together all crust ingredients. press over bottom and up the sides of a 9-inch pie dish. bake until set, 12-15 minutes.

make filling: melt chocolate in a large bowl. set aside. stir together cornstarch and 2 tbs. of brown sugar in a small bowl. whisk together the eggs and the yolks and combine with cornstarch and sugar mixture. stir together milk, cream, salt, and remaining sugar in a heavy bottomed, medium pot. bring to just a boil. slowly whisk in half of milk mixture into half of egg mixture. Whisk this mixture back into the remaining milk mixture and bring to a boil, whisking constantly. Off the heat, stir in the butter and vanilla. Strain through a fine-mesh sieve into the melted chocolate. Whisk to combine thoroughly. Pour into cooled pie crust. Cover the surface with parchment or plastic wrap and chill until set, about 3 hours.

In the meantime, you can whip up the whipped cream ingredients in a cold mixing bowl.

Crust can be baked up to two days in advance and the pie can be chilled, loosely covered, for up to one day.